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From Julian Foad <julianf...@apache.org>
Subject LZ4 compression
Date Mon, 17 Jul 2017 10:40:43 GMT
Evgeny Kotkov wrote (in the 'Proposal: new fsfs.conf properties' thread):
> To improve the situation with slow commits of large binary and, possibly,
> incompressible files I committed a patch (http://svn.apache.org/r1801940)
> that adds initial support for LZ4 compression in the backend.

This sounds amazing!

and in the log message:
> [...] The interoperability is implemented by bumping the format of > svndiff to 2
and the repository file system format to 8. [...]

Can you state simply what facets of Subversion this benefits so far? It 
looks like it is the compression/deltification internal to FSFS, stored 
in rev files, and not exposed outside FSFS, so it affects server speed 
(and thus commit speed) and server storage space. Any significant effect 
on speed of reading the repo (decompression)?

What parts of Subversion could this usefully be extended to affect?
(Speed of compression/deltification performed on the client for commits? 
Size reduction of data sent over the wire to/from new enough clients?)

> Currently, LZ4 compression is enabled if the fsfs.conf file specifies
> compression-level=1, and all other levels still use zlib for compression

Is this just a 'safe' starting point for testing and will we likely 
change this to use LZ4 for all 'compression-level' settings?

- Julian


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